The proposed research is designed to provide a detailed description of the effects of delta-9-tetrahydrocannabinol (THC), the major psychoactive principle in marihuana, upon reproductive endocrine function in the female mammal. Ovariectomized and intact cyclic female rats will be acutely or chronically exposed to low doses of THC and the effects of treatment on pulsatile luteinizing hormone (LH) secretion and the serum concentrations of LH, follicle stimulating hormone (FSH), and prolactin determined by specific radioimmunoassays. Indwelling atrial cannulae will be used to facilitate the withdrawal of multiple small blood samples from individual alert and unrestrained animals in order to obtain hormonal information for an extended period following drug treatment. The techniques of brain stimulation and hypothalamic deafferentiation, and the injection of exogenous luteinizing hormone releasing hormone (LHRH) will be employed to assess actions of THC directly at the level of the hypothalamus and pituitary, respectively. In addition, the effects of THC on the ovulatory surge of LH and on the leuteotropic surges of prolactin will be examined, and functional significance of observed endocrine changes on the reproductive cycle, ovulation, and the maintenance of pregnancy or pseudopregnancy determined.